1. Field of the Invention
The present invention relates generally to drilling systems and, in one particular embodiment, to a drilling system, which may be utilized with an enhanced coring system to obtain 3.5 inch diameter cores in a single pass, which are up to 90 feet long.
2. Description of the Prior Art
There has been a long felt need in the oil and gas industry to be able to provide ninety foot long cores of three and one-half inches, preferably in a single pass. However, for decades, prior art methods have failed to provide this capability. While this capability would be desirable in any size wellbore, this capability would not be expected to be developed for drilling in relatively smaller well bores that range in hole size from seven and three-quarter inches to eight inches in size.
U.S. Pat. No. 6,736,224, issued May 18, 2004, to the present inventor, which is hereby incorporated herein by reference in its entirety, provides a drilling system that teaches how to obtain relatively large diameter cores while drilling/coring small diameter (approximately 6 inch), shallow (less than a few thousand feet) boreholes. However, while the system is now commonly used to obtain relatively large diameter cores in relatively small diameter, shallow wells, the system is limited to shallow holes of a few thousand feet. As well, for this system, the holes must be relatively vertical. Finally, the system is not capable of producing ninety foot long cores of three and one-half inches.
In well bores that are at greater depths (i.e, greater than 7,000 feet) with formations of a higher compressive strength, there remains a significant risk of core loss prior to retrieval. Larger and longer cores could be utilized to improve analytical test results and obtain full samples upon retrieval. For example, having a core diameter of a larger size could improve lost gas analysis tests by creating a larger mass for testing formation fluid content by having a larger mass for analysis.
Various limitations presently prevent obtaining larger and longer diameter cores (i.e., equal to three and one-half inches in diameter and up to ninety feet in length) when drilling well bores that range in hole size from seven and three-quarter inches to eight inches in size. Casing, which was used in shallow wells to obtain large diameter cores, is not practical at greater depths. Presently used API drill pipe for this diameter hole does not have sufficient ID to permit larger diameter cores. Moreover, there was previously no mechanism for creating suitable pipe to handle the coring forces dynamics, which at greater depths, also require a high torque connection and high tensile rating.
Historically when attempting to extract wire line core samples at depths greater than 7,000 ft., an industry available API drill string was utilized in order to achieve such depths. However, in order to maintain an appropriate operating tensile and torsional strength for the drill pipe in a hole size of seven and three quarters to eight inches, the maximum core size diameter achievable using an API drill string is only three inches.
In order to achieve a larger core diameter size (greater than three inches), the internal diameter of standard API, proprietary, or market available drill pipe would be required. This in turn would weaken the pipe and therefore eliminate the pipe as a solution from the very problem it was intended to solve.
The above cited prior art does not disclose suitable solutions to the above discussed problems. As a result, a need remains for a system capable of obtaining larger diameter core samples (equal to three and one-half inches) as well as other drilling operations.
Consequently, those skilled in the art will appreciate the present invention that addresses the above and other problems.